Wednesday, 10 February 2010

x86 BIOS calls used by grub and Linux

The other day I was checking up to see which BIOS calls are used by grub and Linux. I naively believed grub used just a few to get some disk geometry information and to do some reads as well as a little bit of console/keyboard I/O. In fact Grub uses quite a few BIOS calls, namely:

Needless to say, some of these are not used for example, the use of some depend on how the console is configured.

Anyhow, it's quite surprising how much we still rely on core BIOS functionality to get a system up and running. Kudos to Ralph Brown's interrupt list to help me figure out the BIOS int and function code mappings.